Optical digital disk players, such as, for example, audio compact disk (CD) players, are frequently employed in automobiles as a means for providing audio entertainment to vehicle occupants. To enhance the listening experience of vehicle occupants, CD players are typically designed to compensate for anomalies that can be encountered during the audio CD playback process that might otherwise act to interrupt and/or distort the audio produced during the CD playback process. Examples of anomalies that can be encountered during the CD playback process include defects on the CD itself, such as, for example, scratches, smudges, spots, manufacturing defects and/or dirt located on the surface of the CD. Other anomalies that can be encountered during the audio CD playback process include physical shocks and vibrations introduced into the CD player. While anomalies on the surface of audio CDs are not unique to the automotive environment, and can also impact the playback of audio CDs in home or portable CD systems, shock and vibration can be especially prevalent and problematic in an automotive environment in which a vehicle is often traveling at a high rate of speed over a rough road surface.
The anomalies discussed above can act to prevent the pickup mechanism of the CD player from accurately reading and/or interpreting data stored on the CD. In order to reduce the negative impact of such anomalies on the quality of playback, CD player components, including the pickup mechanism and CD player processing circuitry, are typically designed to adapt to anomalies as they are encountered during the playback process. FIG. 1 generally illustrates components typically included in a conventional CD player 20. CD player 20 includes a laser diode (not shown) for projecting a light beam on a surface of a CD 50 placed in the CD player 20. CD player 20 also includes a pickup mechanism 22 for reading signals from the CD 50 and providing them to additional circuitry in the CD player 20 for processing. As shown, pickup mechanism 22 includes a photosensor 11, sled adjustment mechanism 18, tracking adjustment mechanism 14 and focus adjustment mechanism 16. Sled adjustment mechanism 18, tracking adjustment mechanism 14, and focus adjustment mechanism 16 are configured to control the position of pickup mechanism 22 relative to the surface of CD 50. Photosensor 11 includes an array of photo diodes 2, 4, 6, 8, 10 and 12 for detecting light reflected from the surface of the CD 50 and providing analog output signals indicative of the light received by the photo diodes 2, 4, 6, 8, 10 and 12. Photo diodes 10 and 12 are configured to determine the tracking status of pickup mechanism 11. Photo diodes 2, 4, 6, and 8 are configured to read audio data and, in addition, provide signals indicative of the focus status of pickup mechanism 11. Pickup mechanism 22 is configured to be positioned relative to CD 50 by sled adjustment mechanism 18, tracking adjustment mechanism 14 and focus adjustment mechanism 16 in order to accurately read data contained on CD 50.
As shown, the output signals of photo diodes 2 and 6 are combined into a first combined output signal of photo sensor 11, while the output signals of photo diodes 4 and 8 are combined into a second combined output signal of photosensor 11. The first combined output signal, second combined output signal, and output signals provided by tracking photo diodes 10 and 12 are shown provided to Audio/data processing circuitry 30 of CD player 20 for processing. Audio/data processing circuitry 30 is configured to extract high-frequency (HF) audio, focus, and tracking data from the output signals provided by photosensor 11 of pickup mechanism 22. Audio/data processing circuitry 30 is configured to provide audio and/or data to circuitry external to audio/data processing circuitry 30 (not shown) for processing. Audio/data processing circuitry 30 processes extracted HF audio data to provide audio signals that are ultimately provided as audio output to users of the CD player 20. Audio/data processing circuitry 30 is also configured to process focus and tracking data from photosensor 11 to evaluate the operation of pickup mechanism 22 and generate control signals based on the focus and tracking data. The control signals generated by audio/data processing circuitry 30 are provided to drive motor 46, and to sled adjustment mechanism 18, tracking adjustment mechanism 14, and focus adjustment mechanism 16 of pickup mechanism 22, and are used to control those devices to optimize the quality of audio/data output provided by CD player 20 during playback of a CD 50. As shown, the control signals include motor control signals M1, focus control signals F1, tracking control signals T1, and sled control signals S5.
One conventional method typically used to optimize how the CD player 20 generally illustrated in FIG. 1 responds to anomalies is to monitor the audio/data output of the CD player 20 for skip and/or mute conditions during an anomaly that occurs during playback of a CD 50. A skip condition is a condition in which the audio output of a CD player 20 that is playing an audio program is muted for a period of time due to an anomaly (such as, for example, a vibration or scratch), after which period of time the audio output of the CD player 20 resumes at a different point in the audio program than when the mute first occurred. This effectively results in audio material of the CD being skipped as a result of the anomaly, and is generally an undesirable condition. A mute condition is similar to a skip condition, with the main difference being that the CD player 20 resumes playback of the audio program at the same point where the mute first occurred. While undesirable, this condition is less problematic than a skip condition, because little to no audio material is omitted during playback. CD player system designers typically attempt to design a system in which skip and or mute conditions are avoided in spite of the occurrence of anomalies during playback of a CD 50.
As noted above, anomalies can include defects in the disk itself, or environmental factors to which the CD player is exposed during playback. For example, in order to monitor the components and/or signals during a “disk defect” anomaly, a CD played in a CD player 20 may be a test CD including defects on the disk surface, such as scratches and/or dirt. When the CD player 20 encounters these defects on the test CD, the audio/data signals are monitored to determine how well the CD player 20 responds to the given anomaly. In order to monitor the performance of components and/or signals during an “environmental” anomaly, such as vibration, the CD player 20 is vibrated while a CD 50 is played. By monitoring the audio/data signals while the CD player 20 is being vibrated, the response of the CD player 20 to the vibration is determined.
Once the response of the CD player 20 to anomalies has been determined, changes and/or adjustments are made to components and/or circuitry of the CD player 20 in order to attempt to improve the response of the CD player 20 to anomalies. Once changes have been made, the CD player 20 can again be operated in the presence of anomalies, and the audio/data signals monitored to determine if further adjustments are needed to further improve the system performance. In this iterative manner, components and circuitry of CD player 20 can be adapted to provide an improved listening experience for the user of the CD player.
While the aforementioned conventional approach of generating anomalies by means of CDs having defects (test CDs) or by means of physically manipulating the CD player by introducing physical shocks and/or vibrations can provide useful information for optimization of the CD player design, it does have drawbacks. For example, test CDs designed to have specific defects for use in CD player testing can be expensive, and are typically subject to breakdown over periods of repeated use, requiring the purchase of additional expensive testing CDs. In addition, physically vibrating and/or manipulating the CD player while it is playing a CD during repeated testing iterations can expose both the test CD and CD player itself to physical damage. Finally, the need to swap multiple test CDs having various defects in and out of a CD player 20 during iterative test cycles can be time consuming and labor intensive.
What is needed is a CD player testing system and method that reduces the dependence on test CDs and physical manipulation of the CD player being tested, and that reduces the need for repeated insertion and removal of test CDs during iterative test cycles.